1. Field of the Invention
The present invention relates to an image forming method of forming a control image, an image detecting method of detecting it, and an image forming apparatus using the electrophotography or the electrostatic recording method. This image forming apparatus includes a copying machine, printer, and facsimile apparatus.
2. Description of Related Art
A conventional electrophotographic image forming apparatus forms a toner image on a photosensitive member and transfers the image onto a recording medium such as a sheet of paper. Image forming apparatuses which repeat this sequence to achieve multi layer transfer of images onto a recording medium, forming a full-color image are also available. As a development method, such an apparatus adopts a two-component development method.
The full-color image forming apparatus executes control for optimizing the density of a toner image formed every color image so as not to change the hue or tone of a formed image.
More specifically, the density of a patch image formed on a photosensitive member is detected by a density detecting sensor arranged around the photosensitive member. If the detection result is determined to be lighter than a predetermined value, the density of a toner image formed on the photosensitive member is adjusted to darken the image. If the detection result is determined to be darker than the predetermined value, the density of a toner image formed on the photosensitive member is adjusted to lighten the image.
A density detecting sensor 13 uses a near infrared ray LED as a light-emitting element and a photodiode as a light-receiving element. The density detecting sensor 13 detects regular reflection light from a toner image visualized on a photosensitive drum 1. The detected toner image density is controlled by adjusting image forming conditions (toner/carrier density (ratio in weight between toner and carrier), and a charging bias, exposure light quantity, and developing bias for forming an electrostatic latent image on the photosensitive member).
When a low-density toner image is detected by the density sensor, an output from the density sensor becomes unstable and the detection accuracy degrades under the influence of scratches or the like on the surface of the photosensitive drum, resulting in an image forming failure.
It is an object of the present invention to provide an image forming method, image detecting method, and image forming apparatus capable of increasing the density detection accuracy of a detecting sensor regardless of the target density level of a control image.
The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings.